1. Field of the Invention
This invention relates to regulator valves employing an improved metering valve and filter assembly, and to an improved filter assembly and method of manufacturing such an improved filter assembly for use in regulator valve.
2. Description of the Prior Art
The ever increasing requirements for higher purity gases delivered under precisely controlled conditions for use in the analytical, scientific and electronic industries places correspondingly more stringent demands on systems for delivering such gas. Flow regulator valves used in such systems which can initially accurately and dependably control the pressure of gases are known, but these valves may become less reliable with use due in part, to the erosive or abrasive effect on the valve member and valve seat of ultra fine particles in the gas stream. Efforts to remove such fine particles to provide ultra clean or ultra pure gas and to protect and prolong the life of the valves have included the use of a gas filter positioned immediately upstream of the metering valve element. One such filter which has been used commercially employs a cup-shaped, sintered powdered metal filter element having an elongated, generally cylindrical filter body, with the closed end of the cup providing a support or seat for the valve stem spring. Other systems have generally employed disc-shaped filters disposed in the gas stream.
While sintered powder metal filters have been used commercially, they have not been found entirely satisfactory for certain applications. For example, it is difficult to produce entirely uniform filters since the porosity of the filters varies not only with the size of the powdered metal particles, but also with the pressure employed to shape the element and the temperature and duration of heat applied in the sintering operation. Although uniform overall loads can be easily applied in the powdered metal compaction operation, distribution of the powdered material in the mold is not always entirely uniform so that variations in porosity can result. Further, the relatively thin sintered powdered metal filter is inherently relatively brittle, requiring great care in handling and assembly to prevent cracking, splintering or flaking of the material. Further, in use, such filters can "shed" or lose small powdered metal particles which are not completely sintered or which becomes dislodged during handling or use.
Filters formed from other materials have also been used, but they too have not been entirely satisfactory for various reasons in certain applications. For example, where the filter acts as a support for the valve closing spring, substantial strength and dimensional stability is required, but is not always provided by the known materials. For example, shaped metal screens have been used as filters, but the molding, shaping or drawing of woven metal screens results in relative movement of the screen elements or strands and can produce non-uniform screen openings. Further, the woven screen material frequently does not possess the dimensional stability and strength to serve as a valve spring support, thereby complicating the valve design. Accordingly, it is an object of the present invention to provide an improved gas filter for use in a gas control valve, and to provide an improved gas control valve employing such a filter.
It is another object to provide an improved gas filter having high strength and dimensional stability and which is not subject to shedding or cracking as a result of handling.
Another object of the invention is to provide such a filter which is highly uniform in its filtering capacity and which is capable of filtering extremely small particles from the gas stream flowing therethrough.
Another object of the invention is to provide a novel method of producing a gas flow filter.
Another object of the invention is to provide an improved gas regulator valve having an improved gas flow filter.